The invention relates to xerographic process control, and more particularly, to improved xerographic process control using developer to photoreceptor current sensing for adjusting the grid voltage of a charging device.
Xerographic control is well known in the prior art. The art is replete with various sensors and systems for charging control, for exposure and illumination control, for developer control, and for measuring toner concentration and adjusting toner dispensers. For example, U.S. Pat. No. 4,348,099 discloses the uses of test patches, an infrared densitometer, and an electrometer for charge, illumination, toner dispenser, and developer bias control.
One difficulty with prior art systems has often been the need for costly sensors such as infrared densitometers and electrometers. Another difficulty has been the inability to account for significant electrostatic differences between photoreceptor surfaces on different machines and even to account for significant electrostatic differences between different segments of the same photoreceptor surface on a given machine. It would be desirable, therefore, to provide reliable and less costly photoreceptor voltage control to produce higher quality copies over the life of the photoreceptor.
It is an object, therefore, of the present invention to provide new and improved photoreceptor voltage control by sensing developer to photoreceptor current as toner patches are developed and using the sensed current to adjust the grid voltage of a charging scorotron. Other objects and advantages of the present invention will become apparent as the following description proceeds, and the features characterizing the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.